Lipids and pigments in deep-sea surface sediments and interfacial particles from the Western Crozet Basin     

Laurence Pinturier-Geiss  Jeanne Laureillard  Catherine Riaux-Gobin  Joëlle Fillaux  Alain Saliot   《Marine Chemistry》2001,75(4)

Deep-sea sediment samples were collected in the Western Crozet Basin (Indian sector of the Southern Ocean) through Permanently Open Ocean Zone (POOZ), Polar Frontal Zone (PFZ) and Sub-Antarctic Zone (SAZ). Lipid class and fatty acid compositions were investigated to determine the sources and fate of organic matter in the first centimeter of sediment and, above this layer, in the fluff (when present) and particles in the overlying water. The total lipid content varied from 74 to 1033 μg l⁻¹ in the overlying particles and fluffs, and from 24 to 97 μg g⁻¹ dry mass (DM) in surficial sediments. Lipid composition was always dominated by phospholipids in the first centimeter of sediment and often in the overlying particles. The amount of phospholipids (labile compounds representative of fresh material) was compared to the amount of chlorophyll a (Chl a), another compound that is susceptible to rapid degradation. A strong N–S gradient was observed in the distribution of these two compounds, which was attributed to the contrasting hydrodynamic of the study area. The high sedimentation rate in POOZ resulted in better preservation of Chl a in this zone than in other zones of the Crozet Basin (PFZ and SAZ). Phospholipid fatty acids suggested the presence of viable as well as morphologically intact organisms, and these organisms consisted essentially of bacteria with some diatom cysts in the fluff of POOZ. These spores were able to grow in the culture, indicating that they were still viable. Despite the strong hydrodynamic variability, phospholipid fatty acids analysed from the deep-sea surficial sediments were never representative of plankton. This pointed to the extremely labile nature of the phospholipids originally present in planktonic material compared with Chl a, which was always found in overlying particles and surficial sediments.  相似文献   

The IAU 2009 system of astronomical constants: the report of the IAU working group on numerical standards for Fundamental Astronomy     

Brian Luzum  Nicole Capitaine  Agn??s Fienga  William Folkner  Toshio Fukushima  James Hilton  Catherine Hohenkerk  George Krasinsky  G??rard Petit  Elena Pitjeva  Michael Soffel  Patrick Wallace 《Celestial Mechanics and Dynamical Astronomy》2011,110(4):293-304

In the 2006?C2009 triennium, the International Astronomical Union (IAU) Working Group on Numerical Standards for Fundamental Astronomy determined a list of Current Best Estimates (CBEs). The IAU 2009 Resolution B2 adopted these CBEs as the IAU (2009) System of Astronomical Constants. Additional work continues to define the process of updating the CBEs and creating a standard electronic document.  相似文献   

An empirical line list for methane in the 1.26–1.71 μm region for planetary investigations (T = 80–300 K). Application to Titan     

Alain Campargue  Le Wang  Didier Mondelain  Samir Kassi  Bruno Bézard  Emmanuel Lellouch  Athena Coustenis  Catherine de Bergh  Mathieu Hirtzig  Pierre Drossart 《Icarus》2012,219(1):110-128

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Farside explorer: unique science from a mission to the farside of the moon   总被引：4，自引：0，他引：4  

David Mimoun  Mark A. Wieczorek  Leon Alkalai  W. Bruce Banerdt  David Baratoux  Jean-Louis Bougeret  Sylvain Bouley  Baptiste Cecconi  Heino Falcke  Joachim Flohrer  Raphael F. Garcia  Robert Grimm  Matthias Grott  Leonid Gurvits  Ralf Jaumann  Catherine L. Johnson  Martin Knapmeyer  Naoki Kobayashi  Alexander Konovalenko  David Lawrence  Mathieu Le Feuvre  Philippe Lognonné  Clive Neal  Jürgen Oberst  Nils Olsen  Huub R?ttgering  Tilman Spohn  Susanne Vennerstrom  Graham Woan  Philippe Zarka 《Experimental Astronomy》2012,33(2-3):529-585

Farside Explorer is a proposed Cosmic Vision medium-size mission to the farside of the Moon consisting of two landers and an instrumented relay satellite. The farside of the Moon is a unique scientific platform in that it is shielded from terrestrial radio-frequency interference, it recorded the primary differentiation and evolution of the Moon, it can be continuously monitored from the Earth–Moon L2 Lagrange point, and there is a complete lack of reflected solar illumination from the Earth. Farside Explorer will exploit these properties and make the first radio-astronomy measurements from the most radio-quiet region of near-Earth space, determine the internal structure and thermal evolution of the Moon, from crust to core, and quantify impact hazards in near-Earth space by the measurement of flashes generated by impact events. The Farside Explorer flight system includes two identical solar-powered landers and a science/telecommunications relay satellite to be placed in a halo orbit about the Earth–Moon L2 Lagrange point. One lander would explore the largest and oldest recognized impact basin in the Solar System— the South Pole–Aitken basin—and the other would investigate the primordial highlands crust. Radio astronomy, geophysical, and geochemical instruments would be deployed on the surface, and the relay satellite would continuously monitor the surface for impact events.  相似文献   

A less‐is‐more approach to geovisualization – enhancing knowledge construction across multidisciplinary teams     

Catherine Emma Jones  Mordechai Haklay  Sam Griffiths  Laura Vaughan 《International journal of geographical information science》2013,27(8):1077-1093

The ‘less‐is‐more’ concept in interface design for computer applications has recently gained ground. In this article, the concept is adopted for a user‐centered design of geovisualization application. The premise is that using simple and clear design can lead to successful applications with improved ease of use. Over the last three decades, the development of GIS and geovisualization has seen a marked increase in the levels of interaction between the user, the system and the information. However, these enthusiastic advances in technology have not resulted in a significant increase in the number of users.

This article suggests that types of user interaction should not simply emphasize traditional GIS functions such as zooming and panning but move towards interaction based on facilitating the knowledge construction process. Considerations are made for the complexity of the system, the task at hand and the skills and limitations of the users. These elements are particularly important when maps act as the mediators in collaboration with users across disciplinary backgrounds. In such cases, the emphasis on simplicity and usability becomes as important as functionality. In these situations a geovisualization application designed for specific uses can maximize effective development of geographic knowledge.

In this article, a minimalistic design approach to geovisualization is adopted by creating a geographic profiling tool which shifts the emphasis from technological advances or interaction with the map to the interaction elements key to building the spatial knowledge of GIS experts and non‐experts alike. To evaluate this notion of ‘less‐is‐more geovisualization’ the profiling tool is evaluated according to usability matrices: efficiency, effectiveness and learnability. How well the Suburban Profiler contributes to these elements is assessed by conducting a video analysis of the types and forms of user interaction available. The video analysis demonstrates the usefulness and usability of the Suburban Profiler, providing proof of concept for ‘less‐is‐more geovisualization’.  相似文献   

Silver and lead in high-altitude lake sediments: Proxies for climate changes and human activities     

Marion Garçon  Catherine Chauvel  Emmanuel Chapron  Xavier Faïn  Mingfang Lin  Sylvain Campillo  Sarah Bureau  Marc Desmet  Marie-Christine Bailly-Maître  Laurent Charlet 《Applied Geochemistry》2012

High-altitude lake sediments are often used as archives for environmental changes and their chemical and isotopic compositions provide significant constraints on natural and anthropogenic long-term changes that have occurred in their catchment area. Here, trace-element concentrations and Pb isotopes are presented for two sedimentary cores from Lake Blanc Huez in the French Alps, to trace the impact of climate changes and human activities over the Holocene. Lead and Ag contents are very high and clearly dominated by input from a Pb–Ag vein located a few meters from the lakeshore, a vein that also buffers the Pb isotopes. Mining of this vein in medieval times is recorded in the corresponding lake sediments with high Ag content coupled with high Pb/U ratio. These chemical characteristics can be used to constrain the major Holocene climate changes. Significant advances of glaciers next to the lake produced sediments with Ag and Pb concentration peaks and high Pb/U ratios due to accelerated erosion of the Pb–Ag vein, similar to the effects of the medieval mining. In contrast, reduced glacier activity led to the formation of organic-rich sediments with high U and As contents and low Pb/U ratios. More generally, the observed combination of chemical changes could be used elsewhere to decipher environmental changes over long periods of time.  相似文献   

The impact of African aridity on the isotopic signature of Atlantic deep waters across the Middle Pleistocene Transition     

Bruno Malaizé  Elsa Jullien  Amandine Tisserand  Charlotte Skonieczny  E. Francis Grousset  Frédérique Eynaud  Catherine Kissel  Jérôme Bonnin  Svenja Karstens  Philippe Martinez  Aloys Bory  Vivianne Bout-Roumazeilles  Thibaut Caley  Xavier Crosta  Karine Charlier  Linda Rossignol  José-Abel Flores  Ralph Schneider 《Quaternary Research》2012,77(1):182-191

A high resolution analysis of benthic foraminifera as well as of aeolian terrigenous proxies extracted from a 37 m-long marine core located off the Mauritanian margin spanning the last ~ 1.2 Ma, documents the possible link between major continental environmental changes with a shift in the isotopic signature of deep waters around 1.0–0.9 Ma, within the so-called Mid-Pleistocene Transition (MPT) time period. The increase in the oxygen isotopic composition of deep waters, as seen through the benthic foraminifera δ¹⁸O values, is consistent with the growth of larger ice sheets known to have occurred during this transition. Deep-water mass δ¹³C changes, also estimated from benthic foraminifera, show a strong depletion for the same time interval. This drastic change in δ¹³C values is concomitant with a worldwide 0.3‰ decrease observed in the major deep oceanic waters for the MPT time period. The phase relationship between aeolian terrigeneous signal increase and this δ¹³C decrease in our record, as well as in other paleorecords, supports the hypothesis of a global aridification amongst others processes to explain the deep-water masses isotopic signature changes during the MPT. In any case, the isotopic shifts imply major changes in the end-member δ¹⁸O and δ¹³C values of deep waters.  相似文献   

Post-seismic deformation associated with the 2001 Bhuj earthquake     

Pallabee Choudhury  J. K. Catherine  V. K. Gahalaut  Sumer Chopra  Rakesh Dumka  Ketan Singha Roy 《Natural Hazards》2013,65(2):1109-1118

We report the results of GPS measurements of post-seismic deformation due to the 2001 Bhuj earthquake in the Kachchh region, western India. The estimated horizontal velocity vectors in ITRF05 are in the range of 48?C49?mm/year in N46?C50°E. The observed velocity at the Gandhinagar permanent site, a far off site from the earthquake source region and probably unaffected by the post-seismic deformation, is 49?±?1?mm/year in N47°E, which is consistent with the predicted motion of Indian plate at Gandhinagar. At other sites in the source region, transient post-seismic deformation is found to be low; it attenuated rapidly within 3?C4?years of the earthquake and is much low now. Our results support the idea that mantle rheology is weak in the region.  相似文献   

The geodynamic evolution of the South-Tethyan,margin in Zanskar,NW-Himalaya,as revealed by the Spongtang ophiolitic melanges     

Ingrid Reuber  Michel Colchen  Catherine Mevel 《Geodinamica Acta》2013,26(4-5):283-296

Abstract

— The composite nappe of the Spongtang ophiolite is thrust over Mesozoic and Cenozoic sediments of the North-Indian margin and shelf. The ophiolitic peridotiles tectonic-ally overlie a sedimentary melange, the detailed stratigraphy of which reveals the evolution of the South-Tethyan margin from its opening to its closure. The matrix of the melange is dated as Upper Campanian to Lower Eocene. Volcano-sedimentary olistoliths indicate carbonate platform sedimentation associated with alkaline lavas in the Permian, followed by more pelagic sedimentation of Upper Triassic and mid- Cretaceous age. They derived from external platforms near to the Indian shelf, but separated from it. Composite olistoliths of mid to late Cretaceous age, containing Permian elements, are found in the upper Cretaceous to lower Eocene wildflysch. Primary contacts of melange upon serpentinites indicates that the deeply eroded oceanic crust served partly as a substratum for the melange.  相似文献   

Late Holocene record of environmental changes,cyclones and tsunamis in a coastal lake,Mangaia, Cook Islands          下载免费PDF全文

Catherine Chagué‐Goff  Jordan Chi Hang Chan  James Goff  Patricia Gadd 《Island Arc》2016,25(5):333-349

A 4.3 m‐long peat sequence from the shore of Lake Tiriara, Mangaia, Cook Islands, was analyzed using an ITRAX core scanner equipped with a magnetic susceptibility meter. Variations in the elemental profiles, providing insights into long‐ and short‐term environmental changes over the last 3500 years, are supported by grain size data and diatom assemblages. The scattering ratio (Mo Inc/Mo Coh) was evaluated and found to represent a good proxy for organic matter in peat. X‐Ray Fluorescence (XRF) data were processed by principal component analysis that confirmed the distinction of biogenic and detrital phases, organic matter and elements of marine origin. The record preserved in the peat sequence includes a peatland infilling stage followed by alternating drier and wetter periods. A notable steady increase in clay associated with high counts of detrital elements from 2000–1700 cal yr BP is attributed to increased erosion, which is most probably linked with human colonization and/or more intense chemical weathering linked with a wetter climate. Freshwater gastropods (Melanoides sp.), which were possibly introduced by humans, or are native, occupied the wetland during a period of lower water level about 1000–1100 cal yr BP. Short‐term changes in the elemental profiles are often linked with slight coarsening of the inorganic fraction that is, however, only revealed after grain size analysis. Peaks in marine indicators (Br, Cl, S, and/or Ca) associated with marine‐dominated diatom assemblages most probably represent marine incursions through the underground tunnel in the makatea, a fossilized, uplifted coral limestone rim. While none of the marine event units present characteristics typical of cyclone or tsunami deposits, the concurrent or absent peak of detrital elements (Fe, Si, Rb, Ti, K) attributed to increased erosion of the volcanic cone associated with a cyclone is used to distinguish both types of events, as also suggested by principal component analysis.  相似文献